From e97d476c7caab9b7946140c94e5873dc94cb2d9d Mon Sep 17 00:00:00 2001
From: Nikita Smith <git.nikita.smith@gmail.com>
Date: Thu, 22 May 2025 11:35:24 -0700
Subject: [PATCH] test for COMDAT ExactMatch selection

---
 src/torture/torture.c | 77 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)

diff --git a/src/torture/torture.c b/src/torture/torture.c
index 91d7b5cb..465197c7 100644
--- a/src/torture/torture.c
+++ b/src/torture/torture.c
@@ -2217,6 +2217,82 @@ exit:;
   return result;
 }
 
+internal T_Result
+t_comdat_exact_match(void)
+{
+  Temp scratch = scratch_begin(0,0);
+  T_Result result = T_Result_Fail;
+
+  {
+    COFF_ObjWriter *obj_writer = coff_obj_writer_alloc(0, COFF_MachineType_X64);
+    COFF_ObjSection *sect = coff_obj_writer_push_section(obj_writer, str8_lit(".a"), PE_DATA_SECTION_FLAGS|COFF_SectionFlag_LnkCOMDAT, str8_lit("a"));
+    coff_obj_writer_push_symbol_secdef(obj_writer, sect, COFF_ComdatSelect_ExactMatch);
+    coff_obj_writer_push_symbol_extern(obj_writer, str8_lit("TEST"), 0, sect);
+    String8 obj = coff_obj_writer_serialize(scratch.arena, obj_writer);
+    coff_obj_writer_release(&obj_writer);
+    if (!t_write_file(str8_lit("a.obj"), obj)) { goto exit; }
+  }
+
+  {
+    COFF_ObjWriter *obj_writer = coff_obj_writer_alloc(0, COFF_MachineType_X64);
+    COFF_ObjSection *sect = coff_obj_writer_push_section(obj_writer, str8_lit(".a2"), PE_DATA_SECTION_FLAGS|COFF_SectionFlag_LnkCOMDAT, str8_lit("a"));
+    coff_obj_writer_push_symbol_secdef(obj_writer, sect, COFF_ComdatSelect_ExactMatch);
+    coff_obj_writer_push_symbol_extern(obj_writer, str8_lit("TEST"), 0, sect);
+    String8 obj = coff_obj_writer_serialize(scratch.arena, obj_writer);
+    coff_obj_writer_release(&obj_writer);
+    if (!t_write_file(str8_lit("a2.obj"), obj)) { goto exit; }
+  }
+
+  {
+    COFF_ObjWriter *obj_writer = coff_obj_writer_alloc(0, COFF_MachineType_X64);
+    COFF_ObjSection *sect = coff_obj_writer_push_section(obj_writer, str8_lit(".b"), PE_DATA_SECTION_FLAGS|COFF_SectionFlag_LnkCOMDAT, str8_lit("b"));
+    coff_obj_writer_push_symbol_secdef(obj_writer, sect, COFF_ComdatSelect_ExactMatch);
+    coff_obj_writer_push_symbol_extern(obj_writer, str8_lit("TEST"), 0, sect);
+    String8 obj = coff_obj_writer_serialize(scratch.arena, obj_writer);
+    coff_obj_writer_release(&obj_writer);
+    if (!t_write_file(str8_lit("b.obj"), obj)) { goto exit; }
+  }
+
+  {
+    COFF_ObjWriter *obj_writer = coff_obj_writer_alloc(0, COFF_MachineType_X64);
+    U8 text[] = {
+      0x48, 0xC7, 0xC0, 0x00, 0x00, 0x00, 0x00,  // mov rax, $imm
+      0xC3 // ret
+    };
+    COFF_ObjSection *sect = coff_obj_writer_push_section(obj_writer, str8_lit(".text"), PE_TEXT_SECTION_FLAGS, str8_array_fixed(text));
+    coff_obj_writer_push_symbol_extern(obj_writer, str8_lit("entry"), 0, sect);
+    COFF_ObjSymbol *symbol = coff_obj_writer_push_symbol_undef(obj_writer, str8_lit("TEST"));
+    coff_obj_writer_section_push_reloc_voff(obj_writer, sect, 0, symbol);
+    String8 obj = coff_obj_writer_serialize(scratch.arena, obj_writer);
+    coff_obj_writer_release(&obj_writer);
+    if (!t_write_file(str8_lit("entry.obj"), obj)) {
+      goto exit;
+    }
+  }
+
+  int not_exact_match = t_invoke_linkerf("/subsystem:console /entry:entry /out:a.exe entry.obj a.obj b.obj");
+  if (not_exact_match == 0) { goto exit; }
+
+  int exact_match = t_invoke_linkerf("/subsystem:console /entry:entry /out:b.exe entry.obj a2.obj a.obj");
+  if (exact_match != 0) { goto exit; }
+
+  {
+    String8             exe           = t_read_file(scratch.arena, str8_lit("b.exe"));
+    PE_BinInfo          pe            = pe_bin_info_from_data(scratch.arena, exe);
+    COFF_SectionHeader *section_table = (COFF_SectionHeader *)str8_substr(exe, pe.section_table_range).str;
+    String8             string_table  = str8_substr(exe, pe.string_table_range);
+    COFF_SectionHeader *sect          = t_coff_section_header_from_name(exe, section_table, pe.section_count, str8_lit(".a2"));
+    if (sect == 0) { goto exit; }
+    String8             data          = str8_substr(exe, rng_1u64(sect->foff, sect->foff + sect->vsize));
+    if (!str8_match(data, str8_lit("a"), 0)) { goto exit; }
+  }
+
+  result = T_Result_Pass;
+exit:;
+  scratch_end(scratch);
+  return result;
+}
+
 internal T_Result
 t_sect_align(void)
 {
@@ -2378,6 +2454,7 @@ entry_point(CmdLine *cmdline)
     { "comdat_any",           t_comdat_any           },
     { "comdat_no_duplicates", t_comdat_no_duplicates },
     { "comdat_same_size",     t_comdat_same_size     },
+    { "comdat_exact_match",   t_comdat_exact_match   },
     //{ "import_export",        t_import_export        },
   };